Tony Lindgren <tony@xxxxxxxxxxx> writes:
> * Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> [091117 15:41]:
>> During suspend, the kernel timekeeping subsystem is shut down. Before
>> suspend and upon resume, it uses a weak function
>> read_persistent_clock() to determine the amount of time that elapsed
>> during suspend.
>>
>> This function was not implemented on OMAP, so from the timekeeping
>> subsystem perspective (and thus userspace as well) it appeared that no
>> time elapsed during suspend.
>>
>> This patch uses the 32k sync timer as a the persistent clock the 32k
>> sync timer value converted to seconds.
>>
>> NOTE: This does *NOT* handle wrapping of the 32k sync timer, so
>> wrapping of the 32k sync timer during suspend may cause
>> problems. Also, there are not interrupts when the 32k sync
>> timer wraps, so something else has to be done.
>
> Kevin, are you planning to queue this in your PM series for the next
> merge window? In that case Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
>
> If you want me to queue this as a fix for the -rc series, let me know.
I'll queue it for next merge window, thanks.
Kevin
>
>> Reported-by: Jon Hunter <jon-hunter@xxxxxx>
>> Signed-off-by: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx>
>> ---
>> Since v1 of this patch, the signature of this function changed.
>>
>> Also note that forthcoming omap_device patches will depend on this
>> function instead of getnstimeofday() since the timekeeping subsystem
>> is suspended when we want to do omap_device timing measurements.
>>
>> arch/arm/plat-omap/common.c | 19 +++++++++++++++++++
>> 1 files changed, 19 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c
>> index cc050b3..8057966 100644
>> --- a/arch/arm/plat-omap/common.c
>> +++ b/arch/arm/plat-omap/common.c
>> @@ -172,6 +172,25 @@ unsigned long long sched_clock(void)
>> clocksource_32k.mult, clocksource_32k.shift);
>> }
>>
>> +/**
>> + * read_persistent_clock - Return time from the persistent clock.
>> + *
>> + * Reads the time from a source which isn't disabled during PM: 32k sync
>> + * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
>> + *
>> + */
>> +void read_persistent_clock(struct timespec *ts)
>> +{
>> + unsigned long long nsecs;
>> + cycle_t cycles;
>> +
>> + ts->tv_sec = ts->tv_nsec = 0;
>> + cycles = clocksource_32k.read(&clocksource_32k);
>> + nsecs = clocksource_cyc2ns(cycles,
>> + clocksource_32k.mult, clocksource_32k.shift);
>> + timespec_add_ns(ts, nsecs);
>> +}
>> +
>> static int __init omap_init_clocksource_32k(void)
>> {
>> static char err[] __initdata = KERN_ERR
>> --
>> 1.6.5.1
>>
>> --
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